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Orchids (Orchidaceae) are not impossible to grow, but they do require moderate maintenance to stay healthy and look their best. Although losing leaves does not mean that the plant is dead, it is generally not a good sign. If your orchid is losing leaves, you should look into the causes and attempt to correct them.

Identification

Orchids grow in a wide variety of species, but the three most common are moth orchids (Phalaenopsis spp.), Cattleya (Cattleya spp.) and Dendrobium (Dendrobium spp.). Dendrobium orchids are showy and come in a range of colors and are winter hardy to U.S. Department of Agriculture plant hardiness zones 9 through 12. Cattleya orchids are relatively easy to grow, come in all colors except blue, and are winter hardy to USDA zones 10 through 12. Moth orchids, which might be the most familiar from grocery stores, display the typical round-bloomed blossoms arranged in sprays and are winter hardy to USDA zones 10 through 12 as well. You can also grow all of these species as houseplants.

Potassium Deficiency

Check for potassium deficiency. Orchids may be potassium deficient for months but not show outward symptoms. As soon as inflorescences grow and potassium must be moved upward to support the stem and flowers, leaves begin to show signs of deficiency, sometimes falling off. Fertilizer your orchids with a diluted solution that contains potassium and is designed specifically for orchids; these are available at garden centers.

Water Deficiency

Water deficiency is another reason leaves might fall off. Luckily, water deficiency first shows itself in leaves flopping and slowly turning yellow, so if you respond quickly enough, you may not lose them. Water needs vary by species. While Cattleyas can withstand a period of drought, moth orchids do not respond well to it. All orchids, however, should be watered as their growing medium is drying out and should receive enough water so that 20 to 30 percent of it runs out the bottom of the pot.

Fungus

Fungal infection is another reason orchids might be showing signs of stress such as leaf loss. Phyllosticta capitalensis, for instance, commonly attacks Dendrobium orchids but considers all orchids possible hosts. The disease begins with faint spots on the leaves and then small yellow spots, but, if it is allowed to reach later stages, orchids will begin to drop leaves and rot will develop all over the plant. Since this is mainly a disease that attacks growers’ greenhouses, check orchids carefully before buying them to ensure that there is no sign of the disease. If it appears, aggressively remove infected sections of the orchid plant.